For this third interim analysis, 153 pts with dMMR/MSI-H EC and 210 pts with dMMR/MSI-H/POLε-mut non-EC solid tumors (56% colorectal cancer, 11% gastric) were enrolled and treated. Efficacy analysis was performed for 143 dMMR/MSI-H EC and 204 dMMR/MSI-H/POLε-mut non-EC pts who had measurable disease at baseline and ≥6 mo of follow-up. ORRs were 45.5% (dMMR/MSI-H EC) and 43.1% (dMMR/POLε-mut non-EC solid tumors; Table). Probability of PFS at 6, 9, and 12 mo was 49.5%, 48.0%, and 46.4% in dMMR/MSI-H EC and 51.8%, 48.1%, and 46.4% in dMMR/MSI-H/POLε-mut non-EC. Median (m) DOR and mOS were not reached for either cohort. Dostarlimab demonstrated durable antitumor activity across 16 tumor types in pts with dMMR solid tumors...